When I first started putting together this exercise, I was thinking of latchkey children and the fact that no child should every feel lost and alone. But I've since realized that we all need to exercise hospitality, and the newly bereaved, and the overworked are just as likely to take heart.
Now take out your keys and put them in your hand. For just a moment think about the number of times a day you open a door. A car door, a work door, the door to home at the end of the day.....
BEHOLD

Behold,Behold,I stand at the door and knock,knock,knock
Behold, behold,I stand at the door and knock,knock,knock.
If anyone hear my voice,If anyone hear my voice...
And will open,open,open the door I will come in...

Try just for a day, to use your keys as a touchstone.. a prompt to welcome Christ to enter with you and be with you, in the "empty" house, the argumentative meeting,or just to take a ride.
May the Lord be with you....
Tinker